Flame retardant nonwoven composites are needed in a variety of applications like medical garments, drapes and fire fighting suits. Research indicates that 80 to 100 operating room fires alone occur each year, and 10 to 20 of those result in serious injury. The introduction of lasers, and other advanced electrical equipments in surgery today have also greatly increased the potential for fires in the operating rooms.
Existing flame retardant chemicals to manufacture such fibers/fabrics via melt spinning are not environmentally friendly and are also toxic. They also weaken the final fabric properties and have an adverse effect on machinery by initiating metal corrosion. Examples of such flame retardant chemicals that are widely used include phosphorous compounds, metal hydrates and halogenated (brominated) compounds in synergistic combination with antimony oxides.
Nonwovens and nonwoven composites possessing both liquid barrier and flame retardancy are desired in many medical applications like surgical drapes (particularly in opthamology) and operating room accessories. Such materials have to provide a barrier to low surface tension liquids such as isopropyl alcohol while offering flame retardancy simultaneously. Prior to the invention, the combination of flame retardancy and liquid barrier property incorporated in the same nonwoven was hitherto not achievable in a single step process.
Nonwoven fabrics possessing light stability (particularly ultraviolet) are used as substrates to manufacture outdoor covers. Outdoor covers include marine, automobile, bike and recreational vehicle covers. Such covers include protecting the vehicle from wear and tear caused by wind, rain and sunlight.
Nonwovens and nonwoven composites to manufacture substrates for such covers are available in the market. However, it was not possible hitherto to incorporate UV stability and flame retardancy in one step using internal melt additives to produce a nonwoven or nonwoven composite.
To overcome these problems the invention provides a combination of light stability and flame retardancy incorporated into a nonwoven using a non-halogenated melt processable compound. Preferably the compound is a N-alkoxy hindered amine light stabilizer (NOR-HALS).
In general use of alkoxyamine functional hindered amine light stabilizers (NOR-HALS) to improve the flame retardant properties of polyolefins, including polyolefins used in fabrics, is known. For example, published European patent application EP 0792911 A2 to Tennesen discloses a phosphate based flame retardant combined with alkoxyamine functional hindered amine light stabilizer to achieve flame retardant properties that are better than those with phosphates alone. There is no disclosure or suggestion in Tennesen that the light stabilizer alone be used as the only flame retardant.
U.S. Pat. No. 5,393,812 to Haley describes fibers and fabrics, as used clothing, upholstery and carpeting which contain about 0.01 to 3% (preferably 0.2 to 1.0%) by weight of the composition, of a light stabilizer. This patent discloses a polyolefin, a NOR HALS (alkoxy amine functional hindered amine light stabilizers) and a phosphorous flame retardant (col. 2 line 33-40; col. 4 line 62-64). Regular HALS (hindered amine light stabilizers) may be employed additionally or in place of NOR HALS.
U.S. Pat. No. 5,096,950 to Galbo discloses numerous N-OR1 alkoxy hindered amine light stabilizers. This patent also notes that the N-OR1 class of HALS can function in the presence of organohalogenated flame retardants and thiosynergists, unlike prior art hindered amine compounds.
Thus it is a broad object of the invention to provide a nonwoven fabric with both UV stability and flame retardancy having at least one fabric layer. The fabric layer is made of a resin, preferably polyolefinic resin, combined with a non-halogenated melt processable compound that is both flame retardant and UV stable. The compound is preferably a N-alkoxy hindered amine and is combined with a base polyolefinic resin into a homogeneous blend which is then either spunbonded or meltblown to form the fabric layer.
Another object of the invention is to provide a nonwoven fabric of that is alcohol repellant in addition to being flame retardant and UV stable. A melt processable fluorochemical additive is added to the homogeneous blend to impart liquid barrier properties to the fabric layer.
A specific object of the invention is to provide a nonwoven UV stable, flame retardant structure that is environmentally friendly and non-toxic.
Another specific object of the invention is to provide a liquid barrier nonwoven fabric or composite that has flame retardant properties suitable for medical use.
A further object of the invention is to provide an outdoor cover substrate having UV stability and flame retardancy in a single step process.
A further specific object of the invention is to provide a method for making the nonwoven fabric of the invention utilizing melt processable additives without initiating metal corrosion.